1. Field of the Invention
The present invention relates to a heat-exchanger protection structure that protects a heat exchanger, which is mounted on a front portion of a vehicle body, against damage in case of a vehicle crash.
2. Description of the Related Art
A conventional heat-exchanger protection structure is disclosed in Japanese patent Application Laid-Open Publication NO. 2006-21700 and Japanese Utility Model Laid-Open Publication No. 64-6123.
In the former conventional heat-exchanger protection structure, left and right stays fixed on a bumper reinforcement extend in a downward and backward direction of a motor vehicle to have a lower clearance between the stays and a lower portion of a heat exchanger unit. The lower clearance is set shorter than an upper clearance between the bumper reinforcement and the heat exchanger unit. When external force larger than a predetermined value acts on the heat exchanger in the backward direction, one of lower and upper portions of the heat exchanger unit becomes separated from a heat-exchanger supporting panel that supports the heat exchanger unit.
On the other hand, when the bumper reinforcement moves and/or deforms in the backward direction due to a slight collision, the bumper stay moves backward to contact with a lower tank of the heat exchanger unit, releasing the lower portion of the heat exchanger unit from the heat-exchanger supporting panel. This avoids the heat exchanger unit from interference with the bumper reinforcement.
In the latter conventional heat-exchanger protection structure, a plurality of attachment pins or brackets are respectively formed on an upper tank and a lower tank of a heat exchanger as one unit made of plastic material to fix the heat exchanger on a motor-vehicle body frame. The attachment pins/brackets have a fragile portion that is capable of being broken so that damage does not reach the tank when the excessive external force acts on the attachment pins/brackets in case of a vehicle crash.
However, the above known conventional heat-exchanger protection structures have the following problems.
In the former protection structure, the heat exchanger is supported on the heat-exchanger supporting panel as follows.
A lower member of the heat-exchanger supporting panel is formed with two attachment holes for supporting the heat exchanger and two engagement holes for engaging clips. The attachment holes have a U-letter shape. Attachment pins formed on the lower portion of the heat exchanger are inserted into the attachment holes through an elastic insulator, and then the clips are engaged with the lower member to block the openings of the attachment holes.
This structure causes problems in that its manufacturing costs become high, manufacturing processes increase, and variation in support stiffness and faulty engagement of the heat exchanger and the heat-exchanger supporting panel occurs.
In the latter protection structure, the fragile portion of the attachment pin/bracket is broken in case of a vehicle crash to avoid the tank from being damaged. Consequently, the tank can avoid from leakage, but the tank with the broken attachment pin/bracket cannot be reused.
This causes problem in that its repair cost becomes higher.
It is, therefore, an object of the present invention to provide a heat-exchanger protection structure which overcomes the foregoing drawbacks and can surely support a heat exchanger with little variation in support stiffness with low manufacturing cost and avoid the heat exchanger from being damaged in case of a vehicle crash to decrease its repair cost.